As a testing method to obtain critical temperature-stress curve for propagation of brittle crack, the author proposes a notch tensile test of cross welded steel plate. An experiment has been carried out for the quenched and tempered steel “2 H”, having high notch toughness and high tensile strength, such as, 60 kg/mm², and the test result was compared with those of ESSO test and of double tension test with each gradient and flat temperature distribution. The result obtained by the test was very similar to that of double tension test with flat temperature distribution. (cf. Fig. 7) The distinctive features of this test are summarized as follows : 1) The cross welded specimen, having a sharp notch in its high tensile residual stress field, may cause single stage complete fracture under lower applied stress than yield stress. 2) When a brittle transverse weld metal is provided at the location of notch, running crack may propagate to the base metal at the temperature above critical temperature for crack propagation without gradient temperature destribution on the specimen. Therefore, it is easy to apply this test for the steel of excellent notch toughness. 3) By adjusting the length of brittle transverse welded joint, sufficient speed of running crack may be obtained. 4) Fracture stress level of the specimen may be adjustable by preloading at the temperature above critical temperature of crack initiation under low applied stress level. Further investigations should be performed about stress destributions at the propagation field under various loading conditions and also about stress re-destribution during crack propagation.